Synthesis,growth, and characterization of a new NLO material 3-(2,3-dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one

3-(2,3-Dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one (DMPP) a potential second harmonic generating (SHG) has been synthesized and grown as a single crystal by the slow evaporation technique at ambient temperature. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. DMPP crystallizes with orthorhombic system with cell parameters a = 20.3106(8) Å, b = 4.9574(2) Å, c = 13.4863(5) Å, α = 90°, β = 90°, γ = 90° and space group Pca2₁. The crystals were characterized by FT-IR, thermal analysis, UV–vis–NIR spectroscopy and SHG measurements. Various functional groups present in DMPP were ascertained by FTIR analysis. DMPP is thermally stable up to 80 °C and optically transparent in the visible region. The crystal exhibits SHG efficiency comparable to that of KDP.     

Highly diastereoselective tandem photoenolization-hetero-Diels-Alder cycloaddition reactions of o-tolualdehydes in the solid state

The (E)-photoenols generated in situ by photolysis of o-tolualdehydes 1-5 in the solid state react with the precursor aldehydes as dienophiles in a hetero-Diels-Alder cycloaddition fashion to afford trans-3-arylisochromanols in excellent yields and in a high diastereoselectivity. An examination of the reactivity of three different classes of rationally designed aldehydes shows that the tandem enolization-Diels-Alder cycloaddition occurs in the solid state efficiently for aldehydes whose (E)-photoenols (i) are more stable than their corresponding benzocyclobutenols and (ii) are not sterically congested. However, rapid cyclization to benzocyclobutenols is found to be the sole pathway for sterically encumbered (E)-enols derived from aldehydes 6-8. Given that the execution of heteromolecular reactions in the solid state is a challenge, the results obtained with simple crystalline o-tolualdehydes are remarkable and the strategy involving in situ generation of a dienol in the crystal lattice of a dienophile to achieve hetero-Diels-Alder reaction in a highly diastereoselective manner is heretofore unprecedented. In the context of enormous interest in tandem/domino reactions in contemporary synthetic organic chemistry, the results observed with o-tolualdehydes exemplify successful execution of tandem reactions in the solid state.